1. Field of the Invention
This invention relates in general to certain new and useful improvements in light diffusing lenses for light fixtures, and more particularly, to an improved light diffusing lens which permits a wide angle of light dispersion thereby permitting a dispersion of light with a resultant lighting of areas previously uncovered by dispersion of light with prior art light diffusing lenses.
2. Brief Description of the Prior Art
Most light fixtures used in overhead lighting environments and particularly, most overhead fluorescent light fixtures are generally constructed of a metal frame having a downwardly facing opening which usually receives and is enclosed by a conventional light dispensing lens. In some cases, the fixture has a lower surface which is flush with a ceiling and in other constructions, the fixture may extend downwardly from the ceiling by a relatively small dimension. However, fixtures which are typically constructed of metal or plastics, are opaque to light and are designed only for light distribution from the downwardly facing light emitting opening.
The conventional light diffusing lens or so-called "diffuser" typically comprises a flat sheet such as a plastic sheet, which is supported by an inwardly struck peripheral rim at the periphery of the light fixture. Thus, the lens is usually co-planar with the surface of the ceiling. The actual source of the light, such as fluorescent lamps, are generally recessed above the surface of the lens.
It is conventionally believed that in order to obtain optimum light efficiency in a given area, such as a room, most light from an overhead light fixtures should be directed downwardly. As a result, no effort is made to direct light to the ceilings or upper portions of the side wall of a given space such as a room. With a given size light source, it is generally assumed that light dispersion should occur at angles of no greater than 45.degree. from the vertical planes at the edge of a light fixture. Therefore, the overall included angle of light dispersion from many overhead light sources is about 90.degree.. In some cases, light dispersion did occur at about 65.degree. outwardly from plans at each of the vertical edges of the lens. Thus, and in these cases, maximum light dispersion is about 130.degree.. In either case, whether light disperses at angles of 45.degree. with respect to vertical planes at the edges of the lens, or 65.degree., it is apparent that upper portions of a room and most of the ceiling remains unlighted, except by reflected light. As a result, there is relatively low lighting levels on the ceiling and upper portions of the vertical walls of a room.
Generally, all prior art lenses utilize a relatively thin sheet of plastic material, such as an acrylic plastic, which is translucent as to somewhat cloud or hide the fluorescent lamps. However, since the lens is very closely spaced with respect to the lamps, there is usually a harsh strong light emanating from the light fixture. Many light dispensing lens producers attempt to use a stippled outer surface. However, even the stippled outer surface does not fully reduce the harshness of the light and further, does not provide any greater light distribution than a non-stippled outer surface. There are some attempts to also use a lens having a prismatic surface effect. However, and here again, the lenses all comprise a relatively flat sheet located at the face of the structure.
There have been attempts to use light diffusing lenses with linear serrations for purposes of directing light. Generally, this attempt to use linear serrations resided in a lens having a peripherally-extending vertical wall along with a flat bottom wall. The vertically-extending peripheral wall had linear serrations with surfaces directed downwardly so that the light passing through the vertical wall was, in effect, directed downwardly. Clearly, light from the bottom wall would be directed downwardly with some side dispersion as for example, at angles of 45.degree. to 65.degree. from the edges of the lens. However, here again, this type of lens was primarily constructed so as to ensure a large concentration of downwardly directed light with very little interest in lighting areas other than those immediately beneath the light.
Most conventional light fixtures have a relatively short vertical depth, that is, vertical dimension, often times due to the fact that there is only a limited amount of space in the ceiling area in which a light fixture is mounted. Thus, the conventional lenses which are now used are in the nature of a flat sheet and are located in very closely spaced relationship to the light source, such as the fluorescent lamps. As a result, the light which is dispersed from the conventional light fixture is usually relatively harsh. Moreover, one looking into a light fixture through the light translucent lens can almost always observe the lamps and the sockets of that fixture.
Harsh lighting condition has a particularly pronounced effect on work stations where one must use a computer screen or otherwise examine information on any other type of raster pattern screen. This harsh lighting condition results in a so-called "glare" on the screen of the computer generating considerable eye fatigue. There have been many attempts to produce computer screens which reduce the amount of glare. However, it has also been found that in an attempt to reduce glare, resolution of the screen is also concomitantly reduced. Consequently, there is a need to control the overall lighting environment of a room or other work area in which computers and similar raster pattern screens are being employed.
Heretofore, there has not been any effective lens for use with an overhead light fixture which provides a very wide angle light distribution and effectively permits the generation of a soft light condition in an entire room environment without sacrificing light efficiency and which also permits substantial light generation without glare.